A castle lantern feature, or lantern tower, is a raised architectural crowning structure pierced with windows or openwork designed to flood interior halls with natural light, vent smoke from central hearths, or serve as an elevated nighttime beacon.

Structural and Architectural Design:
Placement: Positioned at the highest point of a castle, typically capping the central keep, a grand hall, or an apex tower.

Openings: Feature large arched windows, Gothic tracery, or open vertical slots that pierce all sides of the stone structure to let light pass completely through.

Crowning Roofs: Topped with specialized cupolas, miniature pyramidal roofs, or detailed decorative finials.

Historical and Functional Roles:
Illumination and Ventilation: Acted as an early vertical skylight system, letting daylight reach deep into multi-story spiral staircases or great halls while safely venting smoke from interior floor fires.

Navigational Beacons: Served as functional lighthouses or watchtowers during the Middle Ages, where braziers or open fires hung between stone arches to guide friendly ships or travelers safely toward a fortified city or coastal stronghold.